Authentication
Authentication is the process of proving that you're who you say you are. This is achieved by verification of the identity of a person or device. It's sometimes shortened to AuthN. The Microsoft identity platform uses the OpenID Connect protocol for handling authentication.
Authorization
Authorization is the act of granting an authenticated party permission to do something. It specifies what data you're allowed to access and what you can do with that data. Authorization is sometimes shortened to AuthZ. The Microsoft identity platform provides resource owners the ability to use the OAuth 2.0 protocol for handling authorization, but the Microsoft cloud also has other authorization systems such as Entra built-in roles, Azure RBAC, and Exchange RBAC.
Multifactor Authentication
Multifactor authentication is the act of providing another factor of authentication to an account. This is often used to protect against brute force attacks. It's sometimes shortened to MFA or 2FA. The Microsoft Authenticator can be used as an app for handling two-factor authentication. For more information, see multifactor authentication.